What shall I do about my weed-infested lawn? Shall I spade it and start over again from scratch?
If I spade up the whole lawn and carry off all of the crabgrass, will that pesky weed reappear next year?
Is there some way to renovate my old lawn without digging it up again?
These are but a few of the frantic requests I receive from homeowners about this time every year.
There are, of course, solutions to most of these problems, but some are not easy to carry out.
Ways Of Killing Weeds
First, let me stress that there are no shortcuts or secret practices for achieving a thick, velvety lawn.
Good lawns result from proper and careful preparation and regular attention based on tried and tested maintenance practices.
I’d like to tell of one way of killing weeds and weed seeds: before starting a new lawn or renovating an old one.
Using Calcium Cyanamide
The method involves using the chemical calcium cyanamide, sold as Lawn and Garden Cyanamid.
It has the unusual property of destroying weed seeds and young weeds and, at the same time, supplying nitrogen and lime to the soil.
The nitrogen supplied by cyanamid is sufficient for the lawn for the fall season.
Every 1000 square feet should also receive 20 pounds of 20% superphosphate or 15 pounds of 5-10-5 fertilizer to encourage root growth.
For every 100 pounds used, cyanamid also supplies the equivalent of 70 pounds of lime.
Controlling Weeds Using Cyanamid
Last fall on Long Island, I witnessed an impressive demonstration of the effectiveness of cyanamid in controlling weeds and producing fine turf. I also learned a lot of things about cyanamid.
The demonstration was set up for homeowners by my friend, Jim McFaul, of the Nassau County (New York) Farm Bureau in cooperation with the Nassau County Department of Parks.
The procedure followed by Mr. McFaul is now being widely advocated by the manufacturer of cyanamid and is based on many years of scientific and practical tests.
Free Cyanamid
It has been well established that heavy applications of calcium cyanamide will severely burn and consequently kill weed seeds near and on the soil surface.
Once the cyanamid is added to soil and is moistened, “free” cyanamid is formed, which is toxic to seeds and growing plants.
This “free” cyanamid kills both germinated and ungerminated weed seeds. Because it is unstable, it soon breaks down to ammonia and nitrate nitrogen which are then used as plant nutrients.
Fine Seeding The Lawn
Because a three-week period must elapse to be fine seeding the lawn, the best time to use cyanamid is in early August.
The lawn can be seeded in early September and well-established before winter.
Once a vigorous stand of grass is obtained, weeds are less of a problem because they cannot compete with the resulting thick stand of grass.
To produce a weed-free seedbed for lawn grasses, the ground must be thoroughly prepared about a month before seeding is scheduled.
Granular Cyanamid
This should include complete grading and leveling so that further cultivation is not required after the cyanamid is applied.
The granular cyanamid is then evenly applied to the smooth surface of the soil at the rate of 5 pounds per 100 square feet.
A quart container holds 2 pounds of cyanamid. On level areas, it is left undisturbed, but on slopes, it should be lightly raked in.
Three weeks should then elapse to allow the cyanamide to kill the weed seeds and to lose its toxic effects.
Water Is Necessary
Because water is necessary for the proper action of the material, the soil should be kept moist by frequent sprinklings, particularly if no rains fall in the interim.
After the three-week waiting period, the area should be seeded and the soil surface disturbed as little as possible.
Because only the weeds in the top inch of the soil are destroyed, the soil below this level should not be disturbed.
Seven Steps To A Weed-Free Lawn
At the expense of sounding repetitious, here are seven steps to follow for a weed-free lawn.
These are to be followed when preparing new lawns this fall or for renovating old lawns with few good types of grass, which are in poor condition and overrun by crabgrass and other weeds.
- Measure carefully the area to be made into the lawn. Estimate and purchase the following supplies for every 1000 square feet:
- 5 pounds of high-quality grass seed,
- 15 pounds of a complete chemical fertilizer such as 5-10-5 or 20 pounds of 20 % superphosphate, and 50 pounds of cyanamid
- Turn over or mechanically till the soil or the old sod and weeds, applying the amount of fertilizer or superphosphate recommended by local lawn specialists.
Half of the fertilizer or all of the superphosphate can be spread over the surface before turning the soil.
The remainder of the fertilizer is spread over the turned soil and raked in when the soil is pulverized and leveled. This is also the time to add any topsoil needed to fill low spots in your lawn.
- Spread the required amount of cyanamid evenly either by hand or with a garden fertilizer spreader over the smooth seedbed.
Remember that an uneven distribution of cyanamid will result in erratic weed control.
Do not spread cyanamid any closer than 2’ feet from the edge of the root spread of trees and shrubs.
- Rake the cyanamid lightly with a rake to bring it into intimate contact with the soil. Do not rake it in too deeply, or it will lose its effectiveness.
- After lightly raking in the cyanamid, water the soil thoroughly to a depth of an inch. If no rains fall in the waiting period, water once a week to a depth of one inch.
- Three weeks after applying the cyanamid, rake the soil surface very lightly, just enough to break up the crust.
Be extremely careful not to turn up the deeper layers of soil, as this will bring to the surface weed seeds that the cyanamid has not killed.
- Sow good quality grass seed according to standard procedures. Rake the seed lightly and roll the area to bring the seed in close contact with the soil.
Water to ensure seed germination and seedling establishment and follow proper cutting, aeration, and fertilization practices.
Renovating Old Lawns
According to technical representatives of the manufacturer of Lawn and Garden Cyanamid, the following procedure can be used in early August on an old lawn without turning over the soil and sod:
- Measure the area carefully.
- Mow the lawn closely and then water the well to a depth of 4 inches.
- Rake off the old growth and scratch the surface well.
- Scatter the cyanamid evenly at 5 pounds for every 100 square feet of the surface.
- Then use an iron rake to bring the cyanamid into close contact with the soil.
- Allow standing for 3 weeks, occasionally watering to keep the soil moist.
- In the interim, undesirable grasses and weeds (as well as what remains of desirable grasses) are burned off, and nitrogen and lime are supplied.
- After the three weeks waiting period, soak the soil surface well, then rake the surface lightly and seed the area in the standard manner.
- Rake or roll to put the seed into intimate contact with the soil and water until the grass is established.
Lawn and Garden Cyanamid is available in 10, 25, and 50 lb. packages for lawn and other garden uses. Additional details on its use are supplied with each package.
44659 by P. P. Pirone